Controlling supramolecular complex formation on the surface of a monolayer-protected gold nanoparticle in water.

A combination of hydrophobic and electrostatic interactions drives the self-assembly of a large number of small molecules on the surface of a monolayer-protected gold nanoparticle. The hydrophobic interactions originate from the insertion of an aromatic unit in the hydrophobic part of the monolayer. This is evidenced by a shift in the emission wavelength of the fluorogenic probe upon binding. Up to around 35 small molecules can be simultaneously bound to the monolayer surface at micromolar concentrations in water. It is shown that an understanding of the supramolecular interactions that drive complex formation on the monolayer surface provides unprecedented control over the supramolecular chemistry occurring on the surface. By taking advantage of the different kinds of noncovalent interactions present in different probes, it is possibile to displace one type of surface-bound molecule from a heteromeric surface selectively. Finally, it is also possible to catch and release one type of surface-bound molecule selectively.